Exceptional Endeavour marks U.S. Assembly Complete on Station

by Chris Gebhardt

As Endeavour works through Flight Day 4 (FD4), the historic milestone of delivering and attaching the final component for the U.S. segment of the ISS has been completed, with the installation of the premiere scientific experiment to the Station: the Alpha Magnetic Spectrometer 2. Meanwhile, Endeavour performed above and beyond expectations during her triumphant final ascent to space Monday morning.

U.S. Assembly Complete: Delivery and Installation of AMS-02:

Beginning their day at 22:56 EDT Wednesday, Endeavour’s crew is scheduled to grapple the AMS-02 (Alpha Magnetic Spectrometer -02) – a device which will search the universe for evidence of dark matter, dark energy, and anti-matter – Thursday using Endeavour’s SRMS (Shuttle Remote Manipulator System).

Shortly after this, at around 02:30 EDT, the SRMS was used to unberth the AMS from Endeavour’s payload bay. Handoff of AMS to the SSRMS (Space Station Remote Manipulator System) commenced at around 03:00 EDT with SSRMS grapple of AMS.

The crew then ungrapple the SRMS from AMS, officially handing the experiment over to the ISS, at around 03:30 EDT.  AMS was then maneuvered to its attachment point on the ISS.

PGSC deactivation on AMS was followed by stage one installation/first stage capture. Stage two installation was completed 05:46 EDT with umbilical mates then secured.

The SSRMS then ungrappled AMS, marking the completion of its permanent installation on ISS.

With AMS securely on the ISS, a major and long-awaited milestone for the International Space Station will be reached: U.S. Assembly Complete!

*Click here for a NASA TV Timelapse Video of the robotic ballet to install AMS-02 on to the ISS*

Assembly of the International Space Station began on December 4, 1998 when Space Shuttle Endeavour launched from the Kennedy Space Center, FL on the STS-88 mission to join the U.S. Unity module with the Russian Zarya control module.

Thus, Endeavour has become the Space Shuttle orbiter that both began construction of the International Space Station and completed U.S. assembly of mankind’s premiere science laboratory.

Additionally, Endeavour has become the Space Shuttle orbiter that has delivered what could arguably be the most important and profound scientific experiment to fly in space.

Over the course of its tenure on the International Space Station, the AMS – for which the STS-134 mission was mandated by Congress to specifically deliver AMS to ISS – will continuously search the universe for evidence of and information on dark matter, dark energy, and antimatter.

Depending on the results AMS beams back to Earth, the experiment holds the potential to fundamentally and profoundly alter our knowledge/understanding of the composition of, interaction of, and function of the elements of the universe and the universe as a whole. and therefore open up a new era of exploration and understanding.

STS-134 Specific Articles: http://www.nasaspaceflight.com/tag/sts-134/

The Final Ascent of Endeavour: A Picture Perfect launch for the baby orbiter:

In all, Endeavour’s ascent Monday morning could only be described as amazingly clean, efficient, and orderly.

Following from the S0007 PRSD (Power Reactant Storage Distribution) system cryo load for Endeavour’s three electricity-producing Fuel Cells, teams were able to get a full load of LO2 (Liquid Oxygen) and LH2 (Liquid Hydrogen) commodities into the 5 cryo tank sets on Endeavour.

At launch, Endeavour carried an LH2 load in Tank 1 of 98.8 percent, 99.3 percent in Tank 2, 98.4 percent in Tank 3, 99.3 percent in Tank 4, and 98.4 percent in Tank 5. This translates to an LH2 pound mass (lbm) load of 90.9 lbm in Tank 1, 91.4 lbm in Tank 2, 90.5 lbm in Tank 3, 91.4 lbm in Tank 4,  and 90.5 lbm in Tank 5 for a total pound-mass load of 454.7.

In terms of LO2, Endeavour launched with a 100.5 percent LO2 load in Tank 1, 100.1 percent in Tank 2, 100.1 percent in Tank 3, 100.5 percent in Tank 4, and 100.1 percent in Tank 5.  This translates to a 785 lbm load in Tank 1, 782 lbm load in Tank 2, 782 lbm load in Tank 3, 785 lbm load in Tank 4, and 782 lbm load in Tank 5 for a total pound-mass load of 3,915.

According to the Ascent Summary Report, available for download on L2, “The average prelaunch boiloff rates were 0.058 lbm/hr-tank LH2 and 0.19 lbm/hr-tank LO2.” PRSD tank boiloff rates were nominal and confirmed that the vacuum seal at each tank’s annulus was good.

Prelaunch CPM values were taken and recorded as 2, 4 and 20 mV for Fuel Cell #1, 20, 2, and 32 mV for Fuel Cell #2, and 20, 26, and 38 mV for Fuel Cell #3.

According to the Ascent Summary Report (ASR), an IPR (In Process Review) was recorded and charged to 134V (the STS-134 vehicle). IPR 134V-0064 was recorded to document the following: “During prelaunch, Fuel Cell 1, s/n 106, Cell 90 cold open circuit voltage (OCV) indicated ~1100 mv, which is lower than expected Typical fuel cell OCV after reactant purges is approximately 1140 mV.”

This issue stemmed from an occurrence during Fuel Cell shutdown after the April 29th launch scrub. During the Fuel Cell shutdown, a larger than expected voltage dissipation was observed. The issue was analyzed and reported to be a potential indication of “cell reactant cross-over.”

The Fuel Cell’s history from the OPF flow from February 2010 through February 2011 was reviewed, and all teams were confident that the signature was actually “indicative of ionic shorting as a result of potassium carbonate build up on cell stack exterior and was not [due to] the effects of reactant cross-over in the cell.”

This was the only minor issue to gain mention on the ASR.

Endeavour’s three hydraulic Auxiliary Power Units (APUs) were stared in the following sequence: APU-1 (S/N 304) at 08:51:42 EDT, APU-2 (S/N 311) at 08:51:43 EDT, and APU-3 (S/N 303) at 08:51:44 EDT. Their heater systems worked without issue.

APU-1’s gas generator chamber pressure sensor had previously been observed to have a ~100 psi bias during STS-123. The pressure sensor was “waived” following inspection/testing during ground processing for STS-126. The sensor was stable throughout Endeavour’s ascent on Monday.

The APUs remained active through Endeavour’s ascent and were shutdown in numerical sequence at 09:10:37 EDT, 09:10:51 EDT, and 09:11:03 EDT. APU-1 had a total runtime of 18mins 55secs; APU-2 had a total runtime of 19mins 8secs; APU-3 had a total runtime of 19mins 19secs. Each APU used 49 lbs of fuel during their runtimes.

Following a nominal count and S0007, Endeavour’s three SSMEs (Space Shuttle Main Engines) ignited as expected and hit all of their pre-liftoff checkout targets.

SRB ignition occurred under nominal conditions at T0. First motion/liftoff of Endeavour on her final flight occurred on May 16, 2011 at 08:56:27.985 EDT from Launch Complex 39A at the Kennedy Space Center, FL.

Peak-to-peak lateral acceleration at liftoff was 0.09 g – indicating a nominal liftoff and separation of the SSV (Space Shuttle Vehicle) stack from the MLP (Mobile Launch Platform) with no stud hang-ups. A peak-to-peak lateral acceleration of 0.19 g or high would be a potential indication of a hold-down stud/bolt hang-up.

SRB performance was observed to be nominal with a TDEL_ADJUST value of +0.122 seconds – “within the dead band for Adaptive Guidance and Throttling of +/-0.21 seconds.”

The throttle bucket during first stage flight was a nominal bucket of 104/104/72/104 percent.

“The DOLILU I-Loads were based on the L-3:35hr balloon,” notes the ASR. Max dynamic pressure at Max-Q was ~727 psf. The estimation was based on the L-2:20 hr wind balloon. All atmospheric conditions were within LCC guidelines and within SSP flight experience.

All integrated Guidance, Navigation, and Control (GNC) system performance was nominal throughout ascent, and all three IMUs (Inertial Measurement Units) performed as expected.

RCS (Reaction Control System) forward crew cabin window protect firing was conducted under nominal conditions. Forward thrusters F1U, F2U, and F3U were used for the firing. The firing commenced at 08:58:31.9 EDT and lasted for 2.08 seconds.

A nominal SRB separation was recorded by Endeavour’s onboard computers. SRB separation was visible from long-range ground-based tracking cameras located south of the launch pad.

Following SRB staging, a dual OMS (Orbital Maneuvering System) pod engine firing, called OMS assist, was initiated at 08:58:43.0 EDT. The OMS assist maneuver was completed after 165.4 seconds at 09:01:28.3 EDT. OMS performance was observed to be nominal, less the left OMS fuel totalizer gage which “discontinuously dropped from 87 percent to 46 percent at 136/13:00:10 GMT (09:00:10 EDT) , 14 seconds into the OMS Assist burn.”

The totalize gage remained at this 46 percent indication throughout ascent and the OMS-2 and OMS-3 burns. The discrepancy was noted on previous flights of this OMS pod and was therefore an expected and accepted condition.

During ascent, as Endeavour rose above Earth’s atmosphere, the R5D thruster chamber pressure did not “drop of vacuum,” indicating a possible blockage in the thruster or pc sense tube.

At MET 8mins 23.4 seconds, MECO (Main Engine Cutoff) was commanded. MECO was nominal and all flight performance indications were down center-line with only very small MECO target misses.

External Tank (ET) separation from Endeavour occurred at 09:05:10 EDT. This was followed by the nominal 6-second, 10-second thruster translation manoeuvres by Endeavour. 

The ET photo +X manoeuvre was performed at 09:05:19 EDT. It was a 10.0-second, 4-thruster translation that allowed a camera in Endeavour’s ET umbilical well to capture high resolution photographs of ET-122.

The ET photo pitch over manoeuvre was accomplished at 09:05:20 EDT.

All ascent targets were met during powered SSME flight and no OMS-1 was required.  All MPS (Main Propulsion System) elements performed nominally during the entire launch phase, with no anomalies noted. The GH2 and GOX pressurization systems on ET-122 worked perfectly throughout flight.

The GH2 Flow Control Valves (FCVs) cycled 5, 2, & 5 times, respectively. Post-MECO MPS dumps and vacuum inert were nominal.

OMS-2 was a standard dual engine, straight-feed burn lasting 168.6 seconds. The burn began at 19:33:25.3 EDT and ended at 09:36:13.9 EDT.  OMS-2 deltaV was 259.2 fps and resulted in an orbit of 124.3×175.8 nautical miles. OMS performance during the burn was right down centreline with velocity residuals significantly less than 1 fps in all axes.

Endeavour Trivia:

Endeavour (OV-105) is the only Space Shuttle orbiter to have a calendar date overlap for her maiden voyage and her final flight. Endeavour safely returned to Earth to end her maiden voyage, STS-49, on May 16, 1992 with a landing at Edwards Air Force Base, CA. Exactly 19 years later, Endeavour embarked on her final voyage, STS-134, on May 16, 2011.

Click here for Endeavour’s full history:
Part 1: http://www.nasaspaceflight.com/2011/04/space-shuttle-endeavour-a-new-beginning-part-i/
Part 2: http://www.nasaspaceflight.com/2011/04/ov-105-endeavour-a-long-standing-dream-realized/

Prior to STS-134, the last time a Space Shuttle stack disappeared into a solid cloud deck within 30 seconds of liftoff was STS-123/Endeavour on 13 March 2008. Coincidentally, Endeavour’s pilot on STS-123 was also Greg “Box” Johnson – pilot of Endeavour for STS-134.

Endeavour was also the first Space Shuttle orbiter to launch following the tragic attacks of September 11, 2001.

 During that mission, STS-108, she carried with her to space a tattered and torn American flag recovered from Ground Zero in New York City, a Marine Corps flag recovered from the Pentagon, the American flag that flew over the state capital in Harrisburg, PA on Sept. 11th, the 23 shields of the fallen NYPD officers of that day, patches, posters, & an emblem from the FDNY, patches from the Port Authority of New York and New Jersey, and 6,000 small American flags to honor those lost and those who served in the response and recovery efforts.

Coincidentally, Endeavour’s pilot on STS-108 was Mark E. Kelly – Commander of Endeavour on STS-134. Almost 10 years after STS-108, Endeavour – under the command of Mark E. Kelly – would become the first Space Shuttle orbiter to launch after the master-mind of the September 11th attacks was killed in Pakistan by a U.S. Navy SEAL team.

(Images via L2 and NASA.gov. Extensive coverage is being provided on the news site, forum and L2 special sections – the latter of which is the world’s best front row seat to Shuttle missions. With specific and extensive flight day coverage, from interactive “one stop” FD live coverage in the open forum, to internal documentation, photos, videos and content in the specific L2 FD areas).

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